Use correct OpenSSL thread safety macros on OS X (closes #209) Create an Autoconf test to determine if pthread_t is a pointer or scalar type, and use the appropriate CRYPTO_THREADID_set macro based on the result.

con id = fold (fn nm => fn t :: Type => fn acc => [nm] ~ acc => [nm = t] ++ acc) []

con idT = id [D = int, E = float]

val idV = fn x : $idT => x.E